I am going to start building a pair of Proac 2.5 clones soon and I was wondering if anyone had tried placing the ports on the bottom of the enclosures as in the new Response D25's. How would it affect the tuning of the enclosures if the distance between the speaker bottom and floor was about 1 1/2"?

My experiences with slotted ports at the bottom are all good.
It is also easy to make.
I dunno the difference from a tube though cause I have not compared
my designs with the latter case.
However, it is reasonable to believe that the further from the floor the
less impact any port shape will have on the sound.